Known in the art, there are screening apparatuses used for separating mixed materials, such as loam, sand, gravel or other similar products, into coarse and finer materials with the use of a vibrating meshed screen. The meshes of the screening are sized according to the desired size of the finer materials. Generally, the mixed materials are sieved two or three times for obtaining a suitable quality and are conveyed through the apparatus with belt conveyors or archimedes screws.
For obtaining greater efficiency and for other numerous reasons, such as the greater transportation costs and the local legislations on storage, more and more excavation firms process the top soil and other types of soil on site. Generally, the process consists in directly putting the mixed materials from the ground into the apparatus. This is particularly suitable when the separated materials are used on the site. The same process may also be used in a sand quarry.
Generally, the separating apparatus currently used are bulky and are difficult to be moved. Most of them have problems with large rocks, stumps or wood pieces which affect the separating and may damage the apparatus.
The screening apparatus used in the prior art are generally loaded with a loader dropping the mixed materials into the apparatus. This may lower the efficiency of the apparatus because the screen will be saturated and not able to get all the fine materials which will be rejected by the coarse materials. Some apparatuses have been provided to resolve the above-mentioned drawback, like U.S. Pat. No. 5,082,555 issued on Jan. 21, 1992, which uses a tilting hopper body. Such arrangement is however difficult to use with humid materials which tend to stick together and fall in sequence when the tilt angle is important.